Disputing Election, Pro-reform Marchers Fill Tehran Streets

Shouting "Allahu akbar" (God is great), they converged on Revolution Square, where the moderate former prime minister was expected to call for calm after two days of violent unrest in the capital, which have marked the starkest display of discontent in the Islamic Republic in years.

The crowd -- many wearing the trademark green color of Mousavi's campaign -- was the largest display of opposition unity since Friday's elections ended with Mousavi claiming widespread fraud.

"Mousavi, take back our votes," the marchers chanted as they waited for Mousavi and other pro-reform leaders who back his call for the election result to be overturned.

There was no sign of violence or challenges from security forces, the Associated Press reported. Anti-riot stood by with their helmets off and shields at their sides.

But a witness told Reuters that some Ahmadinejad supporters on motorbikes and armed with sticks clashed with marching Mousavi backers. The witness said there were scuffles between the rival groups and that Ahmadinejad supporters used sticks to hit opponents.

Monday's march came hours after Iran's supreme leader, Ayatollah Ali Khamenei, ordered an examination into Mousavi's claims of vote rigging. But it was unclear how the investigation will proceed.

Mousavi has asked the watchdog Guardian Council to annul the election results, citing irregularities. The Interior Ministry and the president have rejected charges of fraud.

Khamenei, who has upheld the election result, met Mousavi on Sunday and told him to pursue his complaints "calmly and legally," state television said.

The 12-man Guardian Council, whose chairman, Ayatollah Ahmad Jannati, endorsed Ahmadinejad before the vote, said it would rule within 10 days on two official complaints it had received from Mousavi and another losing candidate, Mohsen Rezaie. The council vets election candidates and must formally approve results for the outcome to stand.

The election outcome has disconcerted Western powers trying to induce the world's fifth-biggest oil exporter to curb nuclear work they suspect is for bomb-making, a charge Iran denies.

The European Union plans to demand clarification of Ahmadinejad's victory and voice concern at the treatment of his opponents, Spanish Foreign Minister Miguel Angel Moratinos said after talks in Luxembourg with EU counterparts.

U.S. leaders have reacted cautiously, in the hope of keeping alive President Barack Obama's strategy of engagement with Iran.

On Monday, Ahmadinejad delayed a visit to Russia for a regional summit, but he was expected to arrive there on Tuesday.